The system according to the invention applies particularly to the field of transportation. In today's context, transport is the main focus of concerns relating to energy sources and pollution. As far as energy is concerned, economic imperatives favor the use of energies that replace classical fuels. In terms of pollution, standards are becoming increasingly strict and lead to one focus, which is to encourage the development of new fuels, often called replacement fuels.
Hence there is increasing utilization in particular of liquefied petroleum gas (abbreviated LPG) or natural gas which may be in the gaseous or liquid form. Hydrocarbons such as methane ethane, propane, butane, and natural gas are fuels that meet economic constraints and comply with environmental protection regulations.
Although the use of these hydrocarbons has been in place for a number of years and their combustion in conventional engines presents no major problem, their increasingly widespread use, particularly for utility vehicles such as trucks and buses, is restricted for reasons of storage of hydrocarbons under pressure. This requires hydrocarbon tanks and lines or pipes supplying engines to be at high pressures, which is why, in the majority of cases, steel tanks are used. The major drawback of these tanks is their weight, which is at least the equivalent of the weight of the compressed hydrocarbon when the tank is full.
To remedy this drawback and lighten these tanks, the prior art proposes various types of tanks. The document "Energies nouvelles pour l'automobile" [New Energies for Automobiles] by Jean Orselli, published by Paradigme, presents an overview of the technology employed today.
It was first proposed that the thickness of the metal wall constituting the tank be decreased and that it be reinforced with a strap based on reinforcing fibers and a thermoplastic resin. The pressure resistance properties of the lighter tanks thus obtained are satisfactory but their utilization is limited due to aging which may be accelerated by parameters such as temperature and chemical or photochemical degradation; these parameters can decrease the pressure resistance probably due to creep of the thermoplastic matrix and deterioration of the reinforcing effect of the reinforcing fibers.
Other light tanks proposed in the prior art are based entirely on composite materials and are generally obtained by winding fibers impregnated with thermosetting resin. These tanks sometimes have an intermediate sealing layer based on thermoplastic resin or rubber. This type of tank is efficient at a given moment in time but its dynamic fatigue behavior is less satisfactory after repeated pressurization and decompression cycles; in addition, these tanks are relatively heavy and their practical use is consequently limited by economic issues.
To overcome these disadvantages, patents FR-2,553,860, FR-2,661,447, FR-2,669,396 and FR-2,672,370 of the applicant describe light tanks for storing fluids under pressure, composed of a tubular cylindrical structure which is thin, corrugated, and made of plastic or metal, the hollows of the corrugations being fitted with fibrous reinforcing elements attached by a thermosetting resin, and reinforced lengthwise by an external reinforcing element placed on the outside structure of the tank. In particular, FR-2,661,447 mentions the use of such a structure as a tank for storing fluids under pressure, for example as a pressurized gas tank which can be carried on board a vehicle. However, such a structure takes a long time to fill, particularly for thermodynamic reasons linked to pressurization of the hydrocarbon on filling and to the geometric characteristics of this structure which do not favor evacuation of the heat stored during filling. In fact heating is observed, particularly in the bottom areas of the tank.
It has been discovered that by using a storage tank or tank composed of several containers, for example short, tubular structures connected with each other by a feed device, the heating of the tank while it is being filled is decreased because of the stirring brought about by the distribution of the incoming hydrocarbon flows over several short structures whose total length is equivalent to the length of the single structure normally used.